Recently, instead of a conventional CRT-based television, a television having a plate-shaped image source increases in number. As the image source, for example, a plasma display panel may be used.
For example, a plasma television includes, in its housing: a plasma display panel (hereinafter, it may be referred to as “PDP”.) as an image source, an optical sheet, and various optical films. The optical sheet and various optical films serve to provide an observer with a high quality image. Especially, the optical sheet therefore includes prisms and light-absorbing parts (see Patent Document 1.), wherein the prisms are arranged in parallel along the sheet surface of the optical sheet and transmit therethrough image light from the PDP, and the light-absorbing parts are provided between the prisms and suitably block or reflect image light and external light to improve a contrast or to control ghost.
Recently, in terms of, for example, thinning of a plasma television, in many cases an optical sheet is adhered to a PDP directly or through a certain layer (a direct application method) (see Patent Document 2.). In that case, the provided display device includes: an optical sheet; and an adhesive layer for adhesive purpose, wherein, for example, a display device may comprise an optical sheet 220 having a layer structure as shown in FIG. 18. Namely, an adhesive layer 227, an optical functional sheet layer 221, and a PET film layer 226 are stacked in the order from the PDP 211 side (the left side of FIG. 18) toward the observer side (the right side of FIG. 18). The optical functional sheet layer 221 includes the prisms 222 and the light-absorbing parts 223.
By the above constitution of the optical sheet 220, the direct adhesion of the optical sheet 220 to the PDP 211 becomes possible.
Patent Document 1: Japanese Patent Application Laid-Open No. 2006-189867
Patent Document 2: Japanese Patent Application Laid-Open No. 2006-350324